This invention relates to catheter assemblies in general and, more particularly, to catheter assemblies known in the art as over-the-needle catheter assemblies.
Such catheter assemblies are now well known and are provided for inserting a catheter into a patient's blood vessel, generally for the purpose of administering fluids therethrough. The catheter generally extends co-axially from the distal end of a catheter hub. The hub, having a lumen therethrough, is open at its proximal end to receive an introducer needle. The introducer needle is inserted through the proximal end of the hub and through the catheter, with the distal end of the needle, usually provided with a sharpened piercing end, protruding from the distal end of the catheter. The proximal end of the needle is generally affixed to a needle hub.
When the assembly is ready to use for inserting the catheter into a patient's blood vessel, the distal end of the needle hub is usually seated into the proximal end of the catheter hub. The piercing end of the needle is employed to pierce the blood vessel and the catheter is then urged distally over the needle and seated into the blood vessel. At this point, the needle is withdrawn from the catheter by separating the catheter hub from the needle hub and withdrawing the needle proximally from the catheter.
Normally, during the process of removing the needle, one hand of the user, e.g., the nurse, is occupied with occluding the patient's blood vessel to prevent excessive blood flow. Accordingly, the removal of the needle and, more difficulty, the separating of the needle hub from the catheter hub, must be accomplished with one hand.
Several techniques have been developed by users for effecting such one handed separation. Most commonly, the thumb, or in some cases another finger of one hand, is placed upon the catheter hub while one or more of the remaining fingers of such hand grips the needle hub. The thumb and gripping fingers are then moved apart to separate the two hubs. Such techniques may be employed with over-the-needle catheter assemblies such as are disclosed in U.S. Pat. No. 3,352,306 to S. Hirsch; U.S. Pat. No. 3,406,685 to E. A. May; Czechoslovakian Pat. No. 77,010 to J. H. Waelsch.
Several prior suggestions have been made for catheter assemblies which will facilitate the one-handed separation of catheter hub from needle hub. Generally, such suggestions employ a projection extending outwardly from the surface of the catheter hub which the thumb, or other digit, may engage to effect separation. Examples of such assemblies with outwardly extending projections are U.S. Pat. No. 3,348,544 to B. Brown; U.S. Pat. No. 3,454,006 to A. J. Langdon; U.S. Pat. No. 3,515,137 to L. S. Santomieri; U.S. Pat. No. 3,595,230 to G. M. Suyeoka, et al; U.S. Pat. No. 3,714,945 to V. F. Stanley; and French Pat. No. 1,534,118 to M. J. Salem.
In providing such outwardly extending projections, two conflicting criteria have rendered prior suggestions less than totally satisfactory. Firstly, it is highly desirable that, when applying a digit to the catheter hub to effect separation, such digit does not contaminate the proximal end of the catheter hub in that it is this surface which will come into contact with the source of fluid to be administered to a patient. It is understood that, after removal of the needle, the catheter hub is connected to a fluid administration means, e.g., an intravenous administration set. Accordingly, it is a desirable criterion that the projection be positioned at the most distal portion of the catheter hub in order to provide sufficient room for the digit to be applied without such digit contaminating the proximal end of the hub.
Secondly, it is equally desirable to have the distal end of the hub present as smooth a surface as is possible. This is to allow the user, after the catheter has been inserted into the patient, to anchor the catheter against the patient's body. Ordinarily this is done with adhesive tape and an outwardly extending projection at the distal end of the hub will interfere with such taping. Accordingly, it is desirable, from the taping point of view, to have the projection located as close to the proximal end of the hub as is possible.
It can thus be seen that the placement of the projection is a compromise between the sterility and taping requirements and any placement is less than totally satisfactory. In fact, it is preferred that no projection be provided were it not for the need to facilitate separation of the hubs. This is because any projection has the potential to snag against an object and cause the catheter to dislodge.
Accordingly, there is a need for providing, in an over-the-needle catheter assembly, improved means for facilitating one handed separation of the catheter hub from the needle hub.